I'm trying to come up with a word meaning 'addition (before something)' in the sense: His title was 'holiness' but now it must be expressed with the ?something? 'supreme' (such that the title is now 'supreme holiness'). I want it to be clear that 'supreme' has to be added before the term 'holiness'. I thought perhaps 'superaddition', but that's somewhat different.
There might be a technical word that is specific for titles, but the word that seems to come most naturally is:
it must be prefixed with 'supreme'
it must be expressed [adorned?] with the 'supreme' prefix
The words prepended and adjoined also come to mind, but the first is mostly used in computer science, and the second connotes affixing more than prefixing.
I would suggest 'prepend'.
His title 'Holiness' must be prepended with 'Supreme' now.
You could say
Instead of 'holiness' he must be called 'supreme holiness'.
This leaves no room for misunderstanding. The fact that 'supreme' must come before 'holiness' is clear from the concrete term 'supreme holiness' where 'supreme' does indeed appear before 'holiness'